elgg_extract($key, array $array, $default=null, $strict=true)
Checks for $array[$key] and returns its value if it exists, else returns $default.
if(isset($vars['item_class'])) $nav
if(isset($vars['gallery_class'])) $item_class
elgg_instanceof($entity, $type=null, $subtype=null, $class=null)
Checks if $entity is an ElggEntity and optionally for type and subtype.
elgg_pop_context()
Removes and returns the top context string from the stack.
elgg_push_context($context)
Push a context onto the top of the stack.